1. Field of the Invention
The invention relates to the field of electrocardiology and in particular to a method and apparatus for endomyocardial monophasic action potential for early detection of myocardium pathology.
2. Description of the Prior Art
Electrocardiography (ECG) has been used for clinical diagnosis since end of last century. The concept of ECG is that the properties of electrical flow or conductance of the heart is reflected by the body surface electrical signal change. However, it is subject to a number of well known limitations, which arise mainly due to the indirect nature of the measurement. Using microelectronics to directly measure the transmembrane action potential has been practices on the isolated bundles of cardiac fibers or cardiac myocytes in the basic research laboratory for several decades. The changes in the amplitude, time course and the morphology of the action potential characteristically represent the electrophysiology of the cardiac myocytes. Directly measuring the monophasic action potential of the cluster of the myocytes in the endomyocardium using a monophasic action potential (MAP) catheter has been introduced in clinical electrophysiologic testing for more than two decades. Although direct measurement could record the changes of the electrophysiological function of cell membrane in several cardiac myocytes measured in a local region of about 1 mm diameter area, it could not represent the pathophysiological changes in whole heart. The measurement area can not be increased, because too many cells would need to be measured by one electrode. The electrical signal from each cell will interact each other cell to cause a false reading.
To avoid these problems, the prior art solution was to place the electrode in several areas and measure the MAP one by one. This is extremely time consuming, and it is hard to tell the precise position of each of the measurements. Therefore, manual point-to-point measurement is not practical clinically. Also known are electrical signal mappin xe2x80x9csockxe2x80x9d and xe2x80x9ccarpetxe2x80x9d techniques used to map the electrical signals in the epicardium, which is not MAP, for isolated heart preparation and open chest preparation in experimental laboratories. The use of a basket or xe2x80x9clanternxe2x80x9d shape for contact measurements with the endomyocardium has also been attempted by Boston Scientific in a device marketed under the trademark, Constellation catheter. Although the significance was not appreciated, known or practiced in the prior art, the Constellation catheter does not have Ag/AgCl electrodes and the structure of the basket is too soft or limp to obtain good electric contact with the endomyocardium. Consequently, the Constellation catheter is incapable of sensing or recording the MAP and can only record general electrical signals, which have no material diagnostic significance or uniqueness.
The invention is an apparatus for three-dimensional mapping of endomyocardial monophasic action potential (MAP) of endomycardial tissue. The invention comprises a catheter with a distal and proximal end. A wire basket is disposed on the distal end of the catheter. A plurality of electrodes is carried by the basket. The basket is self-expandable by reason of resiliency of the basket to a size and stiffness sufficient to cause the electrodes to make intimate contact with the endomycardial tissue. A flexible cable or other means of electrical communication is disposed in the catheter electrically coupling the plurality of electrodes to the proximal end of the catheter. The flexible cable is comprised of a plurality of flexible wires with one wire being provided to each electrode.
The plurality of electrodes is provided with a Ag/AgCl plating. The number of the electrodes carried by the basket is preferably at least 64. The number of support wires defining the basket is preferably at least 8 and each support wire has at least 8 electrodes. Thin electrical wires carried by the support wires may be connected individually to each of the electrodes or the electrodes may be electrically coupled to each other in different sets. The electrodes are preferably equally or uniformly distributed or arranged on the basket. The basket wires and electrode are insulated. It is to be expressly understood that fewer or more electrodes than 64 are also within the scope of the invention and that the arrangemenit of their mutual connection is arbitrary.
The apparatus further comprises a sheath. The sheath is temporarily disposed over the basket to retain the basket in a collapsed configuration. The sheath is telescopically removable from the basket to allow the basket to self-expand.
The apparatus further comprises an electrophysiological analyzer coupled to the cable to record data from each of the plurality of electrodes and to analyze the data to generate a three-dimensional endomyocardium mapping of endomyocardial monophasic action potential from the plurality of electrodes.
The invention is also defined as a method of determining the myocardium injury lelectrical-pathophysiology of cardiac myocytes. The method comprises the steps of providing a catheter as described above, namely a catheter having with a distal and proximal end, and a wire basket disposed on the distal end of the catheter with a plurality of Ag/AgCl plated electrodes carried by the basket, having a flexible cable disposed in the catheter electrically coupling the plurality of electrodes to the proximal end of the catheter, and a sheath temporarily disposed over the basket to retain the basket in a collapsed configuration. The catheter is disposed into a heart chamber to be mapped. The sheath is telescopically removed from the basket to allow the basket to self-expand in the heart chamber. The basket is self-expandable by reason of resiliency of the basket to a size and stiffness sufficient to cause the electrodes to make intimate contact with the endomyocardial tissue. A heart data signal from each of the plurality of electrodes is recorded and electrophysiologically analyzed to generate a three-dimensional endomyocardium mapping of endomyocardial monophasic action potential from the plurality of electrodes.
In the illustrated embodiment the changes in ptf-V1 and/or the dispersion of Ta-Tc in the body surface 12-lead-electrocardiograms (ECG) is analyzed to determine atrial conduction disturbance associated with myocardium injury. If the ptf-V1 signal equals or exceeds 0.04 or the Ta-TcD signal equals or exceeds 0.06 sxc2xd or both, then a determination is made that there is very likely some myocardium injury or dysfunction, in particular rejection of a heart transplant. The data signal, such as the ptf-V1 and/or Ta-TcD signal, is correlated to an the severity of the cardiac allograft rejection grade.
Accordingly, the endomyocardium monophasic action potential was measured using conventional single electrode MAP catheter in a rabbit heart transplant model. The characteristic changes in amplitude, duration and morphology of the action potential were observed to be able to detect the early rejection with high sensitivity and specificity. The three-dimensional MAP-mapping was able to pin point the area of the myocardium injury induced by a coronary artery occlusion or ablation.